Reading Christoper Alexander’s “A City is Not a Tree” I am realizing the extent to which a service, also, is not a tree, — and the extent to which we, service designers try to force them into tree-structures.

Alexander’s signature move, dating from his earliest work, is what I would characterize as polycentralizing design: identifying the multiple centers and fields of activity, noting where the fields overlap and interact, and how these overlapping fields are embodied and changed — most notably, vivified, strengthened, weakened or killed — by physical form.

Alexander’s eternal enemy is orders that abstract and simplify the complexity of life, and design structures reflecting this simplified abstraction, that are intended only to support this partial understanding, and end up severing vital connections that allow built environments to live.

Why is it that so many designers have conceived cities as trees when the natural structure is in every case a semilattice? Have they done so deliberately, in the belief that a tree structure will serve the people of the city better? Or have they done it because they cannot help it, because they are trapped by a mental habit, perhaps even trapped by the way the mind works — because they cannot encompass the complexity of a semilattice in any convenient mental form, because the mind has an overwhelming predisposition to see trees wherever it looks and cannot escape the tree conception?

I shall try to convince you that it is for this second reason that trees are being proposed and built as cities — that is, because designers, limited as they must be by the capacity of the mind to form intuitively accessible structures, cannot achieve the complexity of the semilattice in a single mental act.

More to come…